Finley, AFAIK, is just an example of the problem I discussed above. We only have upper-class and elite opinions on slavery and is itself rather outdated, given it's from before I was born and I'm old. Sources, translations, and archaeology have changed a lot since then.
Claiming to know what Spartacus was after in detail is pretty silly. It's been in the interest of elites to cast Spartacus as selfishly motivated for a very long time, and indeed during the cold war, failing to do so lead to suspicions of Communist sympathies, because a great number of Communist organisations used Spartacus's name and invoked him. So you see this hilarious spike in "Spartacus was just trying to flee!" stuff from the 60s through the 80s.